Qubits and their challenges
Quantum computers use qubits instead of classical bits to process information, and each qubit can be encoded in the quantum state of a single photon. A single-photon source is a device that delivers exactly one photon in the desired quantum state “on-demand”.
A key component is thus a highly-efficient single-photon source operating on-demand.
A significant challenge is that many indistinguishable qubits (i.e. quantum-mechanically identical to each other) are needed for a computation.
However, in state-of-the-art devices, indistinguishability is increased at the expense of lower efficiency and vice versa, thereby limiting the number of available qubits.
The goal of this project is to demonstrate a new strategy to achieve almost perfect efficiency and indistinguishability simultaneously in the same device, thereby overcoming a significant problem in photonic quantum computation.
Key to sustainable agriculture
Quantum computers can potentially lead to a breakthrough in sustainable ammonia production.
Ammonia is the most widely used fertilizer in the world, but its production is energy intensive and accounts for ≈2% of the global CO2 emission.
It has been demonstrated that a quantum computer using a few hundreds of qubits would be able to elucidate the complex chemical reaction that governs the production of ammonia, and to predict new methods to produce ammonia using less energy.
However, this requires a scalable hardware to generate a sufficiently large number of indistinguishable qubits, which is precisely the goal of this project.
Expectations
“It’s very important to initialize the source in a specific quantum state with high fidelity, so that it can later deliver a stream of indistinguishable single-photons” says Assistant Professor Luca Vannucci who heads the project.
His hypothesis is that a novel excitation protocol based on two detuned laser pulses will be able to excite the source without sacrificing either the efficiency or the indistinguishability.
The main result will be to design and fabricate an innovative device which is compatible with this excitation protocol, and to demonstrate that the hypothesis is indeed correct.
